VR6 - Start Problem (ECU related)

[mattwelcer 0]

I have a odd start problem with my VR6

 

I appear to be getting no voltage at the fuel pump (roughly 0.9V) and the relay doesn't click. If I remove the relay and bridge the large pins 87 + 30 (bypassing the relay) the fuel pump has 12V and runs.

 

So I checked the pins at the relay and the one that appears to be the problem is Position 85 which comes from the ECU and I believe it is ground (wire colour Yellow/Blue).

On the ECU this is PIN 6, if I ground this pin to the battery (using a probe in the back of the pin with a cable directly to the negative terminal on the battery) then you can hear the relay click and the fuel pump runs. Also if the voltage is measured at the pump then it shows battery voltage and the car starts fine. So this to me rules out bad wiring from pin 6 of the ECU to the plug on the back of the relay panel and the relay/fuse panel itself.

 

Today I received another ECU with the same part number, plugged it in expecting everything OK but I still have the same problem.

 

Therefore what tells the ECU to give ground to pin 6? As once the car is started it runs fine and doesn't cut out while driving.

[vw rule 19]

Hello there,

 

Yeah fuel pump relay is in socket 12 (relay normally has n.o 167 on back of it)

This relay has red wire (power) to alarm / immobilizer which cuts power to this relay once armed.

 

Also has red / yellow wire for (power) (fuse 18 = 20amp) to fuel pump and injectors, plus oxygen sensor (O2 sensor)

 

Yellow / blue wire is (earth) from this fuel pump relay to ECU,

but shares earth with fuel pump and pump after run control unit which is grey / black wire,

then comes out of after run control unit as a black wire and goes through heated crank case breather,

Then returns back to fuel pump relay and ECU relay on earth track.

Black wire then connects to alarm / immobilizer as (earth) (note factory alarm / immobilizer)

 

There should be two large brown wires as (earth) which will be attached to car body off fuse box wiring loom,

in fact there are three as one of them goes up to the instrument cluster, I think.

 

ECU relay I think is in socket 3 (relay normally has n.o 109 on back of it)

Black / Brown wire is (earth) and the red / blue wire is (power) from this relay to ECU

Shared earths on this ECU relay are very similar to that of the fuel relay as they share the same circuit.

 

 

Please have a look at this thread http://the-corrado.net/showthread.php?t=81935&p=978986#post978986

 

 

Hope this helps.

 

Si :thumbleft:

[mattwelcer 0]

Thanks for the info Si but not sure how relevant it is as I forgot to mention mine is OBD2 and therefore doesn't have the ECU relay and has the 4pin MAF, coil pack and the electric TB.

 

What i found out last night is that if i disconnect the MAF the fuel pump receives 5Vand the fuel pump relay clicks.

Therefore I guess I need to see if the MAF or MAF wiring is the problem...

[aircraftdoctor 10]

i'm very interested in this situation,i'm having the same problem with my 91 corrado. I had a swap done from 1.8 to vr6 worked well for a while so i did some refurbishment of the corrado and did a rebuild of the vr6. However since that was taking long i bought another vr6 and had it put in and started it now i dont get fuel and the same voltage you see at the pump fuse 18 no pwr and the relay seems not working. I bridged the big pins and the pump came alive like i have never heard it before.That didnt even get it started. I took the fuse box apart used another one same issue. I fail to believe its the ecu cause at one stage i had the engine running dont know what to think. Its very frustrating and its causing me to think about selling the car. What did you find that was causing the problem. I change the harness for the fuel pump on my corrado so that i could use the big pump in the tank. I change the tank also the harness all worked back. Its mind boggling.I bet its something simple. Also you said due to it being an obd2 you dont need the ecu relay in position 3 for relays?I'm willing to fly someone in to make it work,i live in barbados by the way. Let me know whats up.

[mattwelcer 0]

Ok looks like the problem is finally solved! After swapping out the ECU, spark plugs, ht leads, coil pack, MAF, original intake airfilter and cams. It turned out to be the injectors, even though they'd been refurbished a year ago...

[mattwelcer 0]

Oh also swaped air intake temp sensor, blue temp sensor, fuel pressure regulator & fuel pump!